The present invention relates to the medical imaging arts. It particularly relates to black-blood angiography (BBA) using the magnetic resonance imaging (MRI) and computed tomography (CT) medical imaging techniques, and will be described with particular reference thereto. However, the invention will also find application in conjunction with other three-dimensional imaging modalities as well as in other imaging arts in which structures or networks with well-defined characteristics are advantageously differentiated from extraneous imaged structures and background noise.
Catastrophic medical events such as heart attacks and strokes that result from underlying vascular problems are a leading cause of death in the United States. Many Americans also suffer from chronic vascular diseases which degrade quality of life.
Angiography relates to the imaging of blood vessels and blood vessel systems, and as such is a powerful medical diagnostic for identifying and tracking vascular diseases. Angiography enables improved surgical planning and treatment, improved diagnosis and convenient non-invasive monitoring of chronic vascular diseases, and can provide an early warning of potentially fatal conditions such as aneurysms and blood clots.
Angiography is performed using a number of different medical imaging modalities, including biplane X-ray/DSA, magnetic resonance (MR), computed tomography (CT), ultrasound, and various combinations of these techniques. Two-dimensional or three-dimensional angiographic data can be acquired depending upon the medical imaging modality and the selected operating parameters. Many angiographic techniques employ invasive contrast enhanced methodologies in which a contrast agent that accentuates the vascular image contrast is administered to the patient prior to the imaging session. Some techniques, such as MR imaging, are also capable of providing vascular contrast using non-invasive approaches that take advantage of intrinsic aspects of the vascular system, such as the blood motion or flow, to enhance the vascular contrast without an administered contrast agent.
Angiography can generally be categorized into two classes: white blood angiography (WBA) and black blood angiography (BBA). In WBA, the blood vessels (or the blood flowing therein) typically produces a higher image signal than the surrounding non-vascular tissues. For WBA methods such as time of flight MR (TOF-MR) imaging which rely on blood flow velocity to produce the signal enhancement, the WBA typically does not image the full blood vessel lumen. Because blood flow velocity is reduced near the vessel walls, the imaged WBA vessel is often narrower than the physical vessel lumen. Inaccurate WBA lumen imaging is particularly problematic from a clinical perspective because many vascular diseases involve blood vessel stenosis resulting from coating or other degradation of the inside vessel walls. Medical personnel are thus left to interpret whether an imaged blood vessel is exhibiting actual stenosis or simply has been inaccurately imaged by the WBA.
In contrast, BBA shows the vascular regions as signal voids. BBA is capable of more accurately imaging the blood vessel lumens as compared with WBA. BBA is also less sensitive to complex and non-uniform blood flow patterns. However, BBA suffers from several disadvantages relating to the post-acquisition image processing. Blood vessel segmentation of BBA images is complicated because the arterial and venous vascular systems are imaged simultaneously and because, in addition to the vascular structures, other non-vascular regions such as air pockets and bone surfaces typically also appear with dark contrast in the BBA images. These non-vascular dark regions obscure the BBA-imaged vascular structures, especially in minimum intensity projections (MIP's).
Past vessel segmentation methods have proven unsatisfactory for overcoming the problems and generating unambiguous angiographic images from acquired BBA data. The present invention contemplates an improved BBA method and apparatus which overcomes the aforementioned limitations and others.